Optimized lime processing for gold recovery
Gold application
Gold is found in a wide variety of ore types, each requiring tailored processing techniques to ensure optimal recovery. At Lhoist, we supply lime and quicklime products that are critical reagents in gold processing. They act in tandem with cyanide as a lixiviant to recover gold from ore. This is because cyanide can only be used effectively and safely at alkaline pH levels of 10 –11.
Our solutions are essential in all types of gold processing including simple tank leaching, dealing with nuisance copper, copper-gold, heap leaching, refractory gold, lateritic gold, silver recovery from gold plants and telluride-containing gold.
Negative impacts of sodium hydroxide in gold processing
The use of cyanide as a gold lixiviant necessitates maintaining a high pH (typically between 10.5 and 11) to ensure cyanide speciation favors CN⁻ over HCN. This speciation is critical for both the safety and efficiency of cyanide reagent use. Lime is typically the most cost-effective reagent for achieving the target pH in gold processing circuits. However, in some cases, operators choose to use caustic soda (NaOH) instead. This often leads to significant operational issues, including:
• Silica (Si) dissolution and gel formation
• Sodium sulfate accumulation
• Calcium carbonate precipitation and scaling
Each of these issues is discussed in more detail below.